The expansion of an underground mine (e.g. a coal mine) requires digging a tunnel which initially has an unsupported roof. To stabilize and support the roof a roof bolt must be inserted into the roof to provide support. The operator must first drill holes in the roof through the use of a rotatable cutting bit or roof drill bit. A roof bolt is then inserted into each one of the holes.
A common roof drill bit design uses a cutting insert that has been brazed into a slot at the axially forward end of the roof drill bit body. U.S. Pat. No. 5,400,861 to Sheirer discloses various roof drill bits. U.S. Pat. No. 4,603,751 Erickson also discloses various roof drill bits. Applicants hereby incorporate U.S. Pat. No. 4,603,751 and U.S. Pat. No.5,400,861 by reference herein. In addition, the following catalogs published by Kennametal Inc. of Latrobe, Pa. (U.S.A.), which are hereby incorporated by reference herein, disclose roof drill bits: "Kennametal Mining Products", Catalog A96-55(15)H6 (September 1996) [36 pages in length], and "Kennametal Mining Products" Catalog B92-75R(3)M5 (1992) [36 pages in length]. Furthermore, copending U.S. patent application Ser. No. 09/108,181 filed on Jul. 1, 1998 by Massa and Siddle and copending U.S. patent application Ser. No. 08/893,059 filed on Jul. 15, 1997 by Massa and Siddle disclose roof drill bits and cutting inserts for roof drill bits. These two patent applications (Ser. Nos. 08/893,059 and 09/108,181) are hereby incorporated by reference herein.
While the above roof drill bits and the cutting inserts for such roof drill bits have provided satisfactory performance characteristics, there remains room for improvement of the overall performance, as well as room for improvement of certain features of the roof drill bits and the cutting inserts therefor. In this regard, applicants believe that it would be desirable to provide for an improved rotatable cutting bit (e.g., roof drill bit), as well as the cutting insert for the rotatable cutting bit, that presents a cutting insert which has cutting edges with increased strength over earlier cutting inserts.